Genetic correlations between test station and on-farm performance for growth rate and backfat in pigs

Record of performance data taken on Yorkshire pigs on-farm in 123 breeder herds and at a central test station were used to estimate genetic correlations between measures of backfat depth and days to 90 kg on boars at the test station and boars and gilts on-farm. The data involved records on 3,513 station-tested boars, 13,760 farm-tested boars and 28,203 farm-tested gilts from 838, 2,098 and 2,339 sires, respectively. For backfat depth, estimates of genetic correlations were .85 for test station and on-farm boars and 1.04 for test station boars and on-farm gilts. Estimates of genetic correlations between test station and on-farm measures of days to 90 kg were .80 for boars and .74 for boars and gilts. Based on these results, selection of boars on the basis of test station performance for backfat and growth rate would be expected to result in genetic improvement on-farm in both sexes under North American testing and management conditions.     

Estimating milk yield of sows

Hourly milk yields were obtained for nine consecutive hours at d 14 of lactation from 92 crossbred (four breed) sows during their first and second lactations. Additionally, milk yields were obtained at d 14 and 20 of lactation from 175 mature Yorkshire X Landrace sows for nine consecutive hours. Each measurement (4,806 observations) was obtained by weighing the pigs before and after each hourly nursing. These data were examined with the objective of understanding the consequences of reducing the number of measurements obtained from each sow. Four data sets were formed from the measurements, namely, first parity crossbred sows, second parity crossbred sows, d 14 and d 20 milk yields from the Yorkshire X Landrace sows. Differences (P less than .01) among the hourly milk yield estimates found in all four data sets were largely accounted for by the low yield for h 1 and moderate reduction for h 2 compared with the means of nine measurements. There were no significant differences among the hourly yields for h 3 through 5 compared with h 3 through 9 in three of the four data sets. Mean hourly milk yield for first parity crossbred sows, however, increased as additional hourly measurements were taken. Using the mean hourly milk yield estimate of h 3 through 5 would give an unbiased estimate of h 3 through 9, except for first parity sows, and a standard error only 13% greater than the standard error for nine hourly measurements. The shorter procedure would save considerable time and labor.     

Production traits of litters in 2 crossbred Duroc pig lines

Genetics of different pig lines affects litter size, birth weight, and neonatal losses. Low birth weight has long been associated with neonatal losses, but piglet body mass index is reported to show stronger correlation with stillbirth. The aim of this study was to investigate differences in litter size, number of stillborn piglets, piglet BW gain, and body mass index between 2 different Duroc crossbred lines. Landrace × Yorkshire sows in 2 farms (n = 89) were divided into 2 groups on each farm. One group of sows on each farm was inseminated with semen from Landrace × Duroc boars (boar group LD, n = 48), and the other was inseminated with semen from purebred Duroc boars (boar group DD, n = 41). Piglets were monitored from birth to weaning at the age of 5 wk. Litter size in boar group LD was larger than in boar group DD (P = 0.03). Number of stillborn piglets in boar group LD tended to be greater than in boar group DD (P = 0.07). Piglets in boar group DD had a greater BW at birth (P = 0.02) and at 3 wk (P = 0.01) than those in boar group LD. Body mass index from birth to weaning was greater in piglets in boar group DD vs. LD (P < 0.01), and both BW and body mass index of liveborn piglets at birth for both groups combined showed a positive correlation with survival at weaning (P < 0.01). In conclusion, breeding for larger litter size in boar group DD may be one approach to increase the number of vigorous piglets in production, but the inverse relationship between litter size and birth weight was more pronounced for this group than for boar group LD (P = 0.03). Further studies of the impact of litter size on BW gain are necessary before a final conclusion can be reached.     

Genetic analysis of longitudinal measurements of performance traits in selection lines for residual feed intake in Yorkshire swine

A 5-generation selection experiment in Yorkshire pigs for feed efficiency consists of a line selected for low residual feed intake (LRFI) and a random control line (CTRL). The objectives of this study were to use random regression models to estimate genetic parameters for daily feed intake (DFI), BW, backfat (BF), and loin muscle area (LMA) along the growth trajectory and to evaluate the effect of LRFI selection on genetic curves for DFI and BW. An additional objective was to compare random regression models using polynomials (RRP) and spline functions (RRS). Data from approximately 3 to 8 mo of age on 586 boars and 495 gilts across 5 generations were used. The average number of measurements was 85, 14, 5, and 5 for DFI, BW, BF, and LMA. The RRP models for these 4 traits were fitted with pen × on-test group as a fixed effect, second-order Legendre polynomials of age as fixed curves for each generation, and random curves for additive genetic and permanent environmental effects. Different residual variances were used for the first and second halves of the test period. The RRS models were fitted with the same fixed effects and residual variance structure as the RRP models and included genetic and permanent environmental random effects for both splines and linear Legendre polynomials of age. The RRP model was used for further analysis because the RRS model had erratic estimates of phenotypic variance and heritability, despite having a smaller Bayesian information criterion than the RRP model. From 91 to 210 d of age, estimates of heritability from the RRP model ranged from 0.10 to 0.37 for boars and 0.14 to 0.26 for gilts for DFI, from 0.39 to 0.58 for boars and 0.55 to 0.61 for gilts for BW, from 0.48 to 0.61 for boars and 0.61 to 0.79 for gilts for BF, and from 0.46 to 0.55 for boars and 0.63 to 0.81 for gilts for LMA. In generation 5, LRFI pigs had lower average genetic curves than CTRL pigs for DFI and BW, especially toward the end of the test period; estimated line differences (CTRL-LRFI) for DFI were 0.04 kg/d for boars and 0.12 kg/d for gilts at 105 d and 0.20 kg/d for boars and 0.24 kg/d for gilts at 195 d. Line differences for BW were 0.17 kg for boars and 0.69 kg for gilts at 105 d and 3.49 kg for boars and 8.96 kg for gilts at 195 d. In conclusion, selection for LRFI has resulted in a lower feed intake curve and a lower BW curve toward maturity.     

Population parameter estimates for performance and reproductive traits in Polish Large White nucleus herds

Performance test records from on-farm tests of young Polish Large White boars and reproductive records of Polish Large White sows from 94 nucleus farms during 1978 to 1987 were used to estimate population parameters for the measured traits. The number of boar performance records after editing was 114,347 from 3,932 sires, 21,543 dams, 44,493 litters and 1,075 herd-year-seasons. Reproductive performance records of sows involved 41,080 litters from 2,348 sires, 18,683 dams and 1,520 herd-year-seasons. Both data sets were analyzed by using restricted maximum-likelihood programs. The model used for the performance records included fixed herd-year-seasons, random sires, dams and error effects, and covariances for the year of birth of sire and year of birth of dam. The model used for the reproduction data set was the same as the performance data with parity as an additional fixed effect. Estimated heritabilities were .27, .29, .26, .07, .06, .06 for average daily gain standardized to 180 d (ADG), backfat thickness standardized to 110 kg BW (BF), days to 110 kg (DAYS), litter size at birth born alive (NBA), litter size at 21 d (N21) and litter weight at 21 d (W21), respectively. Estimated common environmental effects for the same traits were .09, .10, .09, .06, .07 and .08, respectively. Genetic correlations were .25 (ADG and BF), -.99 (ADG and DAYS), -.21 (BF and DAYS), .91 (NBA and N21), .68 (NBA and W21) and .80 (N21 and W21). The respective phenotypic correlations were .23, -.99, -.20, .88, .75, .86. These population parameters for Polish Large White pigs are similar to those for breeds in other countries.     

Comparisons of specific crosses from Yorkshire-Landrace, Chester White-Landrace and Chester White-Yorkshire sows

One hundred thirty Yorkshire-Landrace (YL), Chester White-Landrace (CL) and Chester White-Yorkshire (CY) F1 crossbred sows were mated randomly to Duroc (D), Hampshire (H), Farmers Hybrid 414 (FH414) or Farmers Hybrid 929 (FH929) boars. These matings produced 321 litters and 3,379 pigs, which were used to determine the effect of sire breeding and dam breeding on preweaning and postweaning performance of the pigs and litters. Litter size born alive, litter size at 56 d, litter weight at 56 d and litter weight per day of age to 100 kg were lower in litters sired by H boars than in those sired by D boars. However, sizes and weights of litters sired by D and H boars were not different from those sired by FH414 and FH929 boars. Litter sizes at birth were larger for litters out of CL and CY sows than those out of YL sows, but significant differences were not found for litter sizes at 21 d, 56 d or at marketing. Pigs sired by H boars were heavier at birth than pigs sired by D boars. Pigs sired by H boars did not differ significantly in weights at 21 and 56 d or in postweaning daily gains or days to 100 kg from pigs sired by D boars. Pigs out of CL dams were heavier at birth, 21 d and 56 d of age than pigs out of CY dams, but did not differ significantly in postweaning gains or in days to 100 kg. Pigs sired by D and H boars had less ultrasonic fat than pigs sired by FH414 and FH929 boars. Pigs sired by FH929 boars were leaner than pigs sired by FH414 boars.(ABSTRACT TRUNCATED AT 250 WORDS)     

Mass selection for increased 200-day weight in a closed line of Landrace pigs

Mass selection for increased weight at 200 d of age was conducted for six generations in a line of Landrace pigs. In the select line, the heaviest nine boars and 18 gilts were selected from each generation to produce the subsequent generation. A contemporaneous control line was maintained by randomly selecting a son from each sire and a daughter from each dam to attain a line size of five boars and 10 gilts. Inbreeding coefficients averaged .182 and .191 for the select- and control-line pigs and .150 and .162 for the select- and control-line dams, respectively, in the sixth generation. The 200-d weights and ultrasound backfat thickness data were collected from 1,022 pigs of 2,181 pigs farrowed. These pigs were sired by 92 boars and out of 210 sows. The generation interval was 13 mo. Twelve traits were studied: weights at birth and at 21, 35, 70, 154, and 200 d of age; daily gains from birth to 35 d, 35 to 70 d, 70 to 154 d, and 154 to 200 d; ultrasound backfat thickness at 200 d; and ultrasound backfat thickness adjusted for 200-d weight. Total weighted cumulative selection differential for 200-d weight was 88.7 kg. Realized heritability for 200-d weight was .26 +/- .08 with an average response of 4.2 +/- 1.3 kg/generation. Correlated responses resulted in increases for all weights and daily gains evaluated. Although ultrasound backfat thickness at 200 d increased in the select line compared to the control line, it was not altered by selection for 200-d weight when adjusted for 200-d weight.     

Effects of mass selection for increased weight at two ages on growth rate and carcass composition of Duroc-Landrace pigs

Duroc boars from a line previously selected over five generations for 200-d weight and those from a randomly selected control line were mated to Landrace sows either from a line previously selected for increased 70-d weight or from a randomly selected pedigree control line. From these matings, 900 pigs were farrowed to examine the effects of crossing lines of pigs mass selected for weight at two ages on growth rate, survival, and carcass composition. A greater (P less than .01) percentage of pigs farrowed survived birth from control-line sows (.974) than from select-line sows (.914). Of those pigs born alive, a greater (P less than .05) percentage of pigs out of control-line sows survived to 21 d (.893) than out of select-line sows (.829). Pigs sired by select-line boars weighed 2.1 kg heavier (P less than .05) at 70 d than pigs sired by control-line boars. Pigs out of select-line sows weighed .11 kg less (P less than .10) at birth and .3 kg less (P less than .10) at 21 d of age but grew .026 kg/d faster (P less than .10) from 70 d to slaughter, weighed 3.9 kg more at 165 d of age (P less than .05), and reached 100 kg 7.0 d sooner (P less than .05) than pigs out of control-line sows. Carcasses from barrows sired by select-line boars had .29 cm more (P less than .10) fat at the 10th-rib than carcasses from barrows sired by control-line boars. Marbling scores were .31 unit greater (P less than .05) and muscle color scores were .25 unit greater (P less than .10) for carcasses from pigs out of select-line sows than for carcasses from pigs out of control-line sows. Selection for increased 70-d weight decreased age at 100 kg without increasing fat deposition. However, survival rates up to 100 kg were reduced. Mass selection for 200-d weight effectively increased 70-d weight, but fat thickness at 100 kg also increased.     

The number of ribs and vertebrae in a Piétrain cross: variation, heritability and effects on performance traits

In a three‐generation experiment with five purebred Piétrain boars and one Landrace, one Large White and 12 Landrace × Large White crossbred sows as founder animals the number of ribs and presacral vertebrae was determined. These numbers were recorded for 111 F₁‐animals and for 2711 F₂‐animals. The number of ribs varied from 13 to 17 and the number of presacral vertebrae ranged from 26 to 30. Means of 15.5 for the number of ribs and 28.6 for the number of vertebrae with a standard deviation of 0.6 for both were calculated. Bayesian heritability estimates were 0.51 for the rib number and 0.62 for the vertebrae number. A phenotypic correlation of 0.76 and a genetic correlation of 0.97 indicated a close relationship of both traits. In additional analyses possible direct or linked effects of rib and vertebrae number on different growth and carcass traits were investigated. Significant effects were found for several traits related to growth, fatness, muscularity and meat quality. Genes for the presacral vertebrae number or linked quantitative trait loci (QTL) accounted for 11.5% of the phenotypic variation in carcass length and for 2.4% of the phenotypic variation in ham weight.     

Osteochondrosis in six breeds of slaughter pigs

Summary The severity and extent of osteochondral lesions have been examined, macroscopically, radiographically as well as histopathologically, in six different breeds of pigs (Belgian Landrace (B), Duroc (D), Dutch Landrace (N), Dutch Yorkshire (G), Hampshire (H) and Piétrain (P)). In these pigs three different levels of feeding were used. Duroc pigs had significantly more severe lesions in the fore limbs than Dutch Landrace (N), Dutch Yorkshire (G), Hampshire (H) and Piétrain (P) pigs, while Belgian Landrace pigs (B) had significant more severe lesions than Dutch Yorkshire (G) pigs. The differences between breeds related more to the degree of severity of the lesions in the articular surfaces of the distal humerus and proximal radius-ulna and in the distal ulnar growth plate than to the presence of the lesions per se. In the hind limbs Belgian Landrace pigs (B) had significantly more severe osteochondral lesions than all other breeds, while Dutch Landrace pigs (N) had significantly more severe lesions than Duroc (D), Dutch Yorkshire (G), Hampshire (H) and Piétran (P) pigs. Pigs with the highest growth rate showed sginificantly more severe osteochondral lesions in the distal ulnar growth plate and in the medial fe,moral condyle than pigs with a more restricted growth rate.     

The Kiel RN experiment: final porcine chromosome 15 mapping results

SUMMARY: A marker experiment with pigs from commercially selected lines is described. One important goal of the experiment was to map the porcine RN locus, a major gene responsible for lowered terminal pH and increased glycogen level in muscle tissue. Experimental families comprised 15 Piétrain × Hampshire boars, of which 14 were heterozygous at the RN locus, 61 homozygous rn(+) /rn(+) sows (five Landrace, 12 Large White, and 44 Landrace × Large White crossbreds), and 509 progenies, 496 of them from heterozygous boars, in total 585 animals. Genotyping was done for seven chromosome 15 microsatellite loci: Sw919, Sw964, S0088, Sw120, Sw906, Sw936, and Sw312. Genotype assignment for the RN locus was based on musculus longissimus dorsi glycogen content. The heterozygosity of markers ranged from 0.47 to 1 in boars and from 0.71 to 0.88 in sows. RN was mapped to the centre of an interval, flanked by Sw120 and the marker pair Sw906/Sw936. Male multipoint distances between RN and Sw120, Sw906, and Sw936 were estimated as 5 cM, 5 cM, and 6.9 cM, respectively. Two-point recombination rates between these markers and RN were 0.05 in all cases, with corresponding lod scores of 52.09, 29.30, and 42.53. Concordances and disconcordances of mapping results in the RN region from different studies are discussed. The male map length of the chromosome region covered was 68.8 cM, in contrast to the female map length of 124.7 cM. Significant differences in recombination rates between sexes were found in intervals Sw919-Sw964, Sw964-S0088, and Sw936-Sw312, but not in the neighbourhood of the RN gene. ZUSAMMENFASSUNG: Es wird ein Kartierungsexperiment mit Schweinen aus kommerziell genutzten Linien beschrieben. Vordringliches Ziel dieses Experimentes war es, das RN-Gen zu kartieren, das für einen erniedrigten End-pH-Wert und einen erh?hten Glykogengehalt im Musklegewebe verantwortlich ist. Die Daten stammen von 15 Hampshire × Piétrain Ebern, von denen 14 am RN Locus heterozygot waren, 61 homozygoten rn(+) /rn(+) Sauen (5 Landrasse-, 12 Large White und 44 Landrasse × Large White Kreuzungssauen) sowie 509 Nachkommen, 496 davon von heterozygoten Ebern, insgesamt also 585 Tiere. Für sieben Mikrosatellitenmarker auf Chromosom 15 wurden die Tiere typisiert: Sw919, Sw964, S0088, Sw120, Sw906 und Sw312. Die Bestimmung der Genotypen am RN-locus erfolgte anhand des Glykogenghalts im Musculus longissimus dorsi. Der Heterozygotiegrad der Marker lag zwischen 0, 47 und 1 bei Ebern und zwischen 0, 71 und 0, 88 bei den Sauen. Als Position des RN-Gens wurde die Mitte eines Intervalles bestimmt, der von dem Marker Sw120 sowie dem Markerpaar Sw906/Sw936 begrenzt wird. Für das m?nnliche Geschlect wurden die Kartenabst?nde zwischen RN und Sw120, Sw906 und Sw936 in einer Mehrpunktanalyse auf 5 cM, 5 cM und 6, 9 cM gesch?tzt. Paarweise Sch?tzungen der Rekombinationsraten zwischen diesen Markern und RN betrugen in allen F?llen 0, 5, mit zugeh?rigen lod scores vol 52, 09, 29, 30 und 42, 53. übereinstimmungen und Diskrepanzen zwischen Kartierungsergebnissen verschiedener Arbeitsgruppen werden diskutiert. Die Kartenl?nge des mit Markern abgedeckten Teils von Chromsom 15 betrug beim m?nnlichen Geschlecht 68, 8 cM, im Gegensatz zu einer L?nge von 124, 7 cM beim weiblichen Geschlecht. Signifikante Unterschiede in den Rekombinationsraten beider Geschlechter wurden in den Intervallen Sw919-Sw964, Sw964-S0088 und Sw936-Sw312 gefunden, nicht jedoch in der Umgebung des RN-Genes.     

Adjustment of pig or litter weights to a 21-day basis in Duroc, Landrace, and crossbred swine

A total of 457 Duroc, 137 Landrace, 131 Duroc x Landrace, and 110 three-and four-breed crossbred pigs were used to estimate multiplicative adjustment factors. Sixty-one Duroc, 24 Landrace, 18 Duroc x Landrace, and 16 three- and four-breed crossbred litters were weighed every 3 or 4 d from 13 to 30 d of age. Prediction equations for estimating pig weights from birth to 30 d and from 13 to 30 d of age are presented. Multiplicative adjustment factors for adjusting pig or litter weights to a 21-d basis for pigs or litters that are weighed between 13 and 30 d of age for different breeds and crossbred combinations are listed. Breed, litters within breed, and pigs within litter x breed effects adjusted for age at weighing were different (P less than .01). Quadratic regression coefficients of weight on age of pig from 13 to 30 d of age did not differ (P greater than .10) from zero for Landrace and three- and four-breed crossbred pigs but were significant for Duroc and Duroc x Landrace pigs.     

Comparisons of specific crosses from Duroc, Hampshire and Spot backcross sows

One hundred 3/4 Duroc-1/4 Landrace (DDL), 3/4 Hampshire-1/4 Landrace (HHL) and 3/4 Spot-1/4 Landrace (SSL) backcross sows were randomly mated to Yorkshire boars to produce a total of 299 litters and 3,271 pigs to determine the effect of dam breeding on preweaning and postweaning performance of the pigs and litters. Litter sizes born and born alive were not significantly different among the three dam breeds studied. However, litter sizes alive at 21 d out of HHL sows were significantly larger than litter sizes out of SSL sows, while the litter sizes out of DDL sows were intermediate to the other two dam breeds. The DDL sows had significantly heavier litters at birth than did SSL sows, but the dam breeds did not differ in the weights of their litters at 21 and 42 d. Pigs out of DDL sows were heaviest at birth but weighed the least at 21 d, while pigs out of SSL sows were heaviest at 21 and 42 d of age. Pigs out of HHL sows weighed the least at birth and at 42 d. There were no significant differences among the dam breeds in the survival rate of their pigs. In the postweaning period, pigs out of HHL sows were the slowest growing and took the most days to reach 100 kg. Feed conversion and average daily feed consumption did not differ significantly among the three dam breeds studied.     

Bayesian analysis of the effect of selection for residual feed intake on growth and feed intake curves in Yorkshire swine

Gompertz growth functions were fitted to longitudinal measurements of daily feed intake (DFI) and BW of 586 boars and 495 gilts from a selection experiment in Yorkshire pigs for residual feed intake (RFI). The selection experiment consists of a line selected for low residual feed intake (LRFI) for 5 generations and a randomly selected control line (CTRL). The objectives of this study were to use Bayesian methods to estimate genetic parameters of the Gompertz curve parameters for DFI and BW, to evaluate the effect of selection for reduced RFI on the Gompertz parameters and shape of curves for DFI and BW, and to develop methodology for quantifying genetic variation at the level of the original phenotypes for DFI and BW based on the Bayesian analysis of the nonlinear model. Separate analyses were done for boars and gilts and for BW and DFI. A hierarchical model was specified in 2 levels: in the first level, the Gompertz function was modeled for each pig, and at the second level, a 3-trait linear mixed model was fitted to the 3 Gompertz parameters (asymptotic value, inflection point, and decay parameter), with fixed effects of line by generation and random effects of additive genetic and environmental effects. Bayesian methods were used to combine the 2 levels of modeling. A total of 30,000 random samples of the posterior distributions after convergence of Markov chains were used for inference. Posterior means of heritability within the first level of the model for the asymptotic value, inflection point, and decay parameter for DFI were 0.74, 0.66, and 0.82 for boars and 0.79, 0.70, and 0.57 for gilts; corresponding estimates for BW were 0.64, 0.58, and 0.60 for boars and 0.46, 0.35, and 0.33 for gilts. For DFI, LRFI boars had a reduced mature DFI (2.91 vs. 3.20 kg/d) and an earlier inflection point (85 vs. 95 d) compared with CTRL boars. For BW, LRFI boars had a lighter mature BW (279 vs. 317 kg), an earlier inflection point (184 vs. 198 d), and a decreased decay parameter (127 vs. 134 d) compared with CTRL boars. In contrast, LRFI gilts had a later inflection point (225 vs. 200 d) and a greater decay parameter (172 vs. 143 d) than CTRL gilts for BW. The other Gompertz curve parameters for DFI and BW for boars and gilts were considered not different between lines, with posterior probabilities of the line differences being greater than zero ranging from 0.1 to 0.9.     

Survival analysis of preweaning piglet survival in a dry-cured ham-producing crossbred line

The aim of this study was to investigate piglet preweaning survival and its relationship with a total merit index (TMI) used for selection of Large White terminal boars for dry-cured ham production. Data on 13,924 crossbred piglets (1,347 litters), originated by 189 Large White boars and 328 Large White-derived crossbred sows, were analyzed under a frailty proportional hazards model, assuming different baseline hazard functions and including sire and nursed litter as random effects. Estimated hazard ratios (HR) indicated that sex, cross-fostering, year-month of birth, parity of the nurse sow, size of the nursed litter, and class of TMI were significant effects for piglet preweaning survival. Female piglets had less risk of dying than males (HR = 0.81), as well as cross-fostered piglets (HR = 0.60). Survival increased when piglets were nursed by sows of third (HR = 0.85), fourth (HR = 0.76), and fifth (HR = 0.79) parity in comparison with first and second parity sows. Piglets of small (HR = 3.90) or very large litters (HR >1.60) had less chance of surviving in comparison with litters of intermediate size. Class of TMI exhibited an unfavorable relationship with survival (HR = 1.20 for the TMI top class). The modal estimates of sire variance under different baseline hazard functions were 0.06, whereas the variance for the nursed litter was close to 0.7. The estimate of the nursed litter effect variance was greater than that of the sire, which shows the importance of the common environment generated by the nurse sow. Relationships between sire rankings obtained from different survival models were high. The heritability estimate in equivalent scale was low and reached a value of 0.03. Nevertheless, the exploitable genetic variation for this trait justifies the inclusion of piglet preweaning survival in the current breeding program for selection of Large White terminal boars for dry-cured ham production.     

Impact of RYR1 genotype of Piétrain boars on litter traits of Czech Large White × Czech Landrace crossbred sows

Summary Piétrain boars of different ryanodine receptor (RYR1) genotypes (NN, Nn and nn, three boars each) were mated with approximately 10 Czech Large White × Czech Landrace sows (genotype NN) each to produce one litter per sow. The progeny of nn boars had a significantly higher individual weaning weight (7.31 kg versus 6.86 kg) and average daily gain from birth to weaning (252 g/day versus 240 g/day) than the progeny of NN boars. Furthermore, piglets from nn boars differed statistically significant also from piglets of boars with the Nn genotype for these two traits. The litters of the NN boars were greater by 0.5 piglets than the litters of the nn boars for the total number of piglets born, piglets born alive and piglets weaned, but the differences were not significant. The Nn genotype showed for all litter size traits and the number of stillborn piglets the best values. The difference between the genotypes Nn and nn was statistically significant at the 0.05 level for the number of piglets born alive and the number of piglets weaned.     

Candidate gene markers for litter size in different German pig lines.

Three diallelic RFLP markers at candidate gene loci for litter size, the estrogen receptor (ESR) gene, the prolactin receptor (PRLR) gene, and the retinol-binding protein 4 (RBP4) gene, were evaluated for their association with the number of piglets born alive in different German pig lines. Genotyping was performed on boars and sows belonging to three different genetic groups from a single farm. Information on 8,336 litter records from 2,159 sows (German Landrace, n = 1,672; Duroc, n = 214; and a synthetic line, n = 273) was used in the analyses with respect to litter size. Growth performance traits were only analyzed for the synthetic line. The ESR locus showed no polymorphism in the tested boars of the German Landrace and Duroc lines. In the synthetic line, the frequency for the A allele was 0.90 and no homozygous BB animal was detected. No significant associations of ESR alleles with number of piglets born alive, backfat thickness, or average daily gain were observed. A new PCR-RFLP was developed for testing the PRLR polymorphism. The frequencies of PRLR allele A were 0.40 in the German Landrace, 0.49 in the synthetic, and 0.82 in the Duroc line. In the Duroc line, a small additive effect of the allele B on litter size was observed. The allelic substitution effect was 0.71 piglets born alive across all parities (P = 0.05). No significant associations of the PRLR locus with litter and growth performance traits were detected. The frequencies of RBP4 allele A ranged from 0.62 in the synthetic line to 0.67 in the German Landrace to 0.85 in the Duroc line. For the genotyped sows of the synthetic line, there was no indication of a favorable effect of the A allele with respect to litter size. Results of this study demonstrate that allele effects differ between lines or populations. This may be due to possible different linkage phases between the marker alleles and the causal mutations in the different lines. The results may also be explained by many minor genes affecting litter size. A selection strategy should be designed for each line separately and should always consider possible pleiotropic effects.     

不同品种、月份、月龄及采精间隔对猪精液品质的影响

为研究不同品种、采精月份、采精月龄和采精间隔等因素对加系公猪精液品质的影响,以及品种、初次采精周龄对精液质量稳定性的影响,本研究以江西某种公猪站79头加系大白猪、长白猪、杜洛克猪种公猪为试验群体,收集2018年12月至2020年12月3 921条精液采集与精液质量数据,通过混合线性模型与方差分析探究各因素对精液量、精液密度、精子活力、总精子数及其稳定性的影响。结果显示,从不同品种对精液质量的影响来看,长白猪精液量和总精子数均高于大白猪、杜洛克猪,但杜洛克猪精液密度高于长白猪、大白猪,杜洛克猪精子活力最低;从不同月份来看,1~3月采精精液密度最高,4~6月采精精子活力最高,10~12月采精精液量和总精子数最高,精液量呈现秋冬多、春夏少的季节变化规律。公猪不同月龄采精,精液质量指标也存在差异,月龄越小精液量越低,但精液密度偏高,精子活力相对较好,在19~24月龄黄金期总精子数最高。不同采精间隔对精液质量有较大影响,采精间隔越长,精液量、精液密度、精子活力和总精子数相对较好,采精间隔为5 d时综合性能最佳,但过长的采精间隔导致精子活力降低。品种影响总精子数稳定性,长白猪、大白猪总精子数稳定性显著优于杜洛克猪（P<0.05）。本研究结果表明,品种、采精月份、采精月龄和采精间隔均会影响公猪精液质量,关注这些因素有助于公猪站制定更完善的生产计划,提高公猪利用率。     

Effects of Duroc, Meishan, Fengjing, and Minzhu boars on productivity of mates and growth of first-cross progeny.

Meishan, Fengjing, Minzhu, and Duroc boars were mated by AI to crossbred gilts to compare the sire breeds for effects on productivity of their mates and performance of their progeny. Gilts were derived from a four-way cross of Chester White, Landrace, Large White, and Yorkshire. At weaning, litters sired by Meishan boars averaged 1.69 and 1.32 more pigs than those sired by Duroc and Minzhu boars, respectively (P less than .05). Pigs sired by Meishan and Fengjing boars averaged 1.2 to 1.8 more nipples than pigs sired by Duroc and Minzhu boars (P less than .05). Minzhu-sired pigs had a lower (P less than .05) survival rate to 14 and 28 d of age than did those sired by Meishan, Fengjing, and Duroc. Fengjing-sired pigs were heavier than Minzhu-sired pigs at birth and heavier than Minzhu- and Duroc-sired pigs at 14, 28, and 56 d of age (P less than .05). At 70 d of age, Meishan-sired pigs were heaviest, followed in order by Fengjing-, Duroc-, and Minzhu-sired pigs. At 98 d of age, Meishan-sired pigs were significantly heavier than all other breed groups and Duroc-sired pigs were significantly heavier than Minzhu-sired pigs. At 126 and 154 d of age, Duroc-sired pigs were heaviest, followed in order by Meishan-, Fengjing-, and Minzhu-sired pigs; all differences were significant. Average backfat thickness of gilts at 99.7 kg was least for Duroc-sired gilts and highest for Meishan-sired gilts. Sire breed groups did not differ significantly in feed efficiency from 70 to 98 d of age. Duroc-sired pigs were the most efficient (P less than .05) from 98 to 126 and 126 to 154 d of age. Results indicate that use of these Chinese breeds in crossbreeding programs will decrease performance traits. This decrease would have to be offset by increases in reproductive efficiency of Chinese sows, use of repartitioning agents, or other management techniques if Chinese pigs are to improve overall production efficiency of a crossbreeding program.     

The effect of two different feed levels on the development of the reproductive organs in boars.

The aim of the present investigation was to study the development of the reproductive organs in boars fed restrictively and fed ad libitum. A total of 120 boars were purchased by the experimental station at 20 kg live weight. Three groups of 4 litter mates were selected after each of 10 A.I. boars (7 Swedish Landrace and 3 Swedish Yorkshire). The dams were unselected sows from pigletproducing herds. Two boar pigs from each litter were allocated at random among 2 treatment groups. One group ( = N) was fed restrictively and the other group (=A) ad libitum. The boars were slaughtered at 90 kg or at 120 kg live weight. The reproductive organs were removed at slaughter and examined.The ad libitum fed boars were about 2 weeks younger at slaughter than those fed restrictively (16.5 and 13.7 days respectively for the 2 weight classes). The weights of the testes were somewhat higher for ad libitum fed than for restrictively fed boars. Out of 94 examined pairs of testes, epididymides, seminal vesicles and bulbo-urethral glands, the left was heavier than the right in 68%, 62%, 48%, and 36%, respectively. Fewer (4/23) ad libitum fed than restrictively fed boars (9/26) had reached puberty at 90 kg live weight. Age at puberty thus seems to be less variable than body size in boars.